1. Field of the Invention
The present invention relates to a discharging device of a recording medium in an image forming apparatus.
2. Description of the Related Art
An image forming apparatus includes a tray unit onto which a recording medium such as paper on which an image is formed is discharged from an inside of the image forming apparatus and stacked. When discharged, the recording medium is fed out in a direction extending along a surface of the tray unit and stacked on the surface of the tray unit at a predetermined position and in a predetermined posture. If recording media are discharged one after another consecutively, the recording media are stacked in sequence on the surface of the tray unit.
If, however, the recording medium has a weak stiffness and thus has a leading end drooping or curling, or otherwise faulty, the recording medium may be discharged with its leading end rounded depending on properties or conditions thereof. In such cases, the leading end of the recording medium being discharged is directed toward the surface of the tray unit, thus contacting the surface of the tray unit at an acute contact angle. This results in a discharge fault occurring, such as the recording medium being stacked out of a predetermined correct position or a predetermined correct posture.
FIG. 27 illustrates an exemplary discharge fault representing rounding of the recording medium. Referring to FIG. 27, an image forming apparatus F includes a discharging roller R and a tray unit T and discharges a recording medium M in a discharging direction P. FIG. 27 illustrates that the recording medium M has a rounded leading end and the leading end of the recording medium M and a surface of the tray unit T define a contact angle α of nearly 90°.
Such an acute contact angle results in a discharging fault occurring, such as the recording medium M being out of the correct stack position, stacked slantwise, or stacked on the surface of the tray unit of the tray unit T in a rolled-up posture.
Japanese Patent Application Laid-open No. 2010-132372 discloses a technique in an image forming apparatus, the technique incorporating fans that generate air flow in an upper portion and a lower portion of a discharging part for discharging the recording medium.
In the technique disclosed in Japanese Patent Application Laid-open No. 2010-132372, while a recording medium is being discharged, a lower fan is rotated to generate a wind force that is used to raise a leading end of the recording medium to thereby ensure that the leading end of the recording medium does not curl downwardly; the instant that a trailing end of the recording medium moves past a discharging roller, the lower fan is stopped and, instead, an upper fan is rotated to generate a wind force that is used to force the trailing end of the recording medium downwardly, so that the recording medium can be stacked on a discharge tray.
The technique disclosed in Japanese Patent Application Laid-open No. 2010-132372, however, involves complicated arrangements. Specifically, for example, the technique requires both the lower fan and the upper fan, the lower fan being rotated to generate the wind force for raising the leading end of the recording medium and the upper fan being rotated to generate the wind force for forcing the trailing end of the recording medium downwardly. In addition, the technique requires that drives for the lower and upper fans be switched between each other.